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 A128556 a(1)=1. a(n) = the smallest positive multiple of d(a(n-1)) that does not occur earlier in the sequence, where d(m) is the number of positive divisors of m. 2
 1, 2, 4, 3, 6, 8, 12, 18, 24, 16, 5, 10, 20, 30, 32, 36, 9, 15, 28, 42, 40, 48, 50, 54, 56, 64, 7, 14, 44, 60, 72, 84, 96, 108, 120, 80, 70, 88, 104, 112, 90, 132, 144, 45, 66, 128, 136, 152, 160, 156, 168, 176, 100, 27, 52, 78, 184, 192, 98, 102, 200, 180 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Is this sequence is a permutation of the positive integers? LINKS Diana Mecum, Table of n, a(n) for n = 1..1000 EXAMPLE a(9) = 24 has 8 positive divisors. So a(10) is the smallest positive multiple of 8 that has yet to appear in the sequence. 8 occurs among the first 9 terms of the sequence, but 16 does not. So a(10) = 16. CROSSREFS Cf. A128555. Sequence in context: A193991 A114107 A175334 * A212485 A077661 A077583 Adjacent sequences:  A128553 A128554 A128555 * A128557 A128558 A128559 KEYWORD nonn AUTHOR Leroy Quet, Mar 10 2007 EXTENSIONS More terms from Diana L. Mecum, May 29 2007 STATUS approved

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Last modified May 20 13:02 EDT 2022. Contains 353873 sequences. (Running on oeis4.)